Nonlocal screening dictates the radiative lifetimes of excitations in lead halide perovskites

TL;DR

This paper uses advanced simulations and theory to reveal how nonlocal lattice screening influences charge interactions in lead halide perovskites, explaining their high efficiency in solar cells.

Contribution

It introduces a nonlocal screening model based on Gaussian field theory that accurately describes charge interactions and exciton properties in lead halide perovskites, surpassing traditional models.

Findings

Reveals repulsive electron-hole interactions at intermediate distances.

Explains small exciton binding energy and low radiative rates.

Clarifies the role of nonlocal screening in high efficiency.

Abstract

We use path integral molecular dynamics simulations and theory to elucidate the interactions between charge carriers, as mediated by a lead halide perovskite lattice. We find that the charge-lattice coupling of MAPbI$_3$ results in a repulsive interaction between electrons and holes at intermediate distances. The effective interaction is understood using a Gaussian field theory, whereby the underlying soft, polar lattice contributes a nonlocal screening between quasiparticles. Path integral calculations of this nonlocal screening model are used to rationalize the small exciton binding energy and low radiative recombination rate observed experimentally and are compared to traditional Wannier-Mott and Fr\"ohlich models, which fail to do so. These results clarify the origin of the high power conversion efficiencies in lead halide perovskites. Emergent repulsive electron-hole interactions provide a design principle for optimizing soft, polar semiconductors.